Stars are massive balls of plasma held together by gravity. Deep inside their cores, nuclear fusion releases enormous amounts of energy and creates many of the elements found throughout the Universe.
A pulsar is a rapidly rotating neutron star that emits beams of electromagnetic radiation. As the beam sweeps across Earth, astronomers can detect regular pulses.
A supernova is an enormous stellar explosion. Some occur when massive stars collapse, while others involve the thermonuclear destruction of white dwarfs.
Giant and supergiant stars can become hundreds or even more than a thousand times larger than the Sun during later stages of stellar evolution.
Sirius is the brightest star in Earth's night sky. It is actually a binary system located about 8.6 light-years away.
Some red supergiants have enormous estimated radii. Their exact sizes are difficult to determine because their outer atmospheres are diffuse and variable.
Strange stars are hypothetical compact objects that could contain strange quark matter. Their existence has not yet been confirmed.
Magnetars are neutron stars with extraordinarily powerful magnetic fields. They can produce intense bursts of X-rays and gamma rays.
A white dwarf is the dense remnant left behind by a low- or medium-mass star after it has exhausted its nuclear fuel.
Brown dwarfs are objects too small to sustain ordinary hydrogen fusion like true stars, occupying a category between giant planets and stars.